1. Field of the Invention
This invention relates to improvements in a steering column for an automotive vehicle, and more particularly to the steering column which is intended to reduce the number of component parts and the number of steps in an assembly process thereby lowering a production cost.
2. Description of the Prior Art
A steering column for an automotive vehicle is a device for causing road wheels for steering to be turned under turning of a steering wheel which is mounted on the steering column. In general, the steering column includes a steering shaft which is rotatably supported inside a jacket tube through bearings. The jacket tube is fixed at its generally intermediate part to a vehicle body through an upper bracket and at its lower end part to the vehicle body through a lower bracket. An intermediate shaft is connected at its upper end portion to the lower end portion of the steering shaft and at its lower end portion to a steering gear box.
Now, at an accidental collision of the automotive vehicle, the following dangerous actions will occur: The front end parts of the vehicle move rearward, and therefore the steering wheel projects toward a driver's side through the intermediate shaft and the steering column (i.e., a rearward projection of the steering wheel under a primary collision). Then, the driver moves forward under reaction of the collision of the vehicle body thereby to come into collision with the steering wheel (i.e., a secondary collision). In order to prevent the above dangerous actions, the steering column has been provided with a structure for absorbing a movement stroke of the steering column at the primary collision and a structure for allowing the steering column to be axially contractible at the secondary collision.
As well known, the former structure in connection with the primary collision is arranged to allow the intermediate shaft to be axially contractible thereby to prevent an axial movement of the steering column. Additionally, the former device may include a stopper provided to the steering column to prevent the steering wheel from being projected to the driver's side. The latter structure in connection with the secondary collision is arranged such that each of the jacket tube and the steering shaft is divided into upper and lower sections which are fitted to be axially slidable to each other thereby allowing each of the jacket tube and the steering shaft to be axially contractible. Additionally, the latter structure includes an energy absorbing member for the steering column. Further, the latter structure may include a device for allowing the upper bracket to be get off from the vehicle body owing to the axial contraction of the steering column when the driver comes into collision with the steering wheel.
However, drawbacks have been encountered in the above conventional steering column as set forth below. That is, the conventional steering column is considerably large in number of component parts in order to provide a contractible function under a load over a predetermined level, and therefore is large in number of steps in an assembly process. Additionally, a high precision has been required for the fitting section between the upper and lower sections of the jacket tube and the steering shaft in order to stabilize a stroke load, thereby raising a production cost of the steering column.
Besides, in the conventional steering column, separate component parts are provided as installation members for the steering column to the vehicle body, the stopper for preventing the steering wheel from projecting toward the driver's side at the primary collision and the energy absorbing member functioning at the second collision, This increases the number of the component parts of the steering column and raises a production cost of the steering column.